JPH04260659A - Production of irreducible dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a process for producing an irreducible dielectric ceramic composition capable of forming a small-sized highly reliable laminated ceramic capacitor. CONSTITUTION:An irreversible dielectric ceramic composition having a perovskite structure expressed by the general formula (A1-xRx)yMO3 is produced by using a water-soluble rare-earth element inorganic compound or a rare-earth element organometallic compound soluble in organic solvent. In the above formula, A is at least one kind of element selected from Ba, Sr, Ca and Mg; R is at least one kind of rare-earth element; M is at least one kind of element selected from Ti, Zr and Sn; and x and y are numbers satisfying the formulas 0.01<=x<=0.020 and 1.002<=y<=1.03.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-reducible dielectric ceramic composition, and more particularly to a method for producing a non-reducible dielectric ceramic composition used as a material for laminated ceramic capacitors and the like.

0002

2. Description of the Related Art When manufacturing a multilayer ceramic capacitor, a sheet-like dielectric material and an electrode material to be an internal electrode are laminated and integrated by thermocompression bonding to obtain a laminated body. This laminate is fired in a predetermined atmosphere to form dielectric ceramic. Then, on the end face of this dielectric porcelain,
A multilayer ceramic capacitor is manufactured by baking an external electrode that is electrically connected to an internal electrode.

The dielectric ceramic composition used in such multilayer ceramic capacitors has the property that when fired under neutral or reducing low oxygen partial pressure, it is reduced and becomes a semiconductor. Therefore, when such a dielectric material is used as a material for a multilayer ceramic capacitor, the internal electrode material must be a high oxygen content material that does not melt at the sintering temperature of the dielectric ceramic material and does not convert the dielectric ceramic material into a semiconductor. It was necessary to use noble metals such as palladium and platinum, which do not oxidize even when fired under pressure. As described above, since an expensive material must be used as the internal electrode material, the manufacturing cost of the multilayer capacitor increases. In particular, in recent years, the miniaturization of electronic components has progressed rapidly, and the trend toward miniaturization and increased capacity of multilayer ceramic capacitors has become noticeable. Therefore, the proportion of electrode material costs in the manufacturing cost of multilayer ceramic capacitors is increasing.

[0004] In order to solve this problem, it is conceivable to use an inexpensive base metal such as nickel as the internal electrode material. However, when such base metals are used as internal electrode materials and fired under conventional conditions, the electrode materials become oxidized and do not function as electrodes. In order to use such a base metal as an electrode material, it must not turn into a semiconductor even when fired in a neutral or reducing atmosphere with a low oxygen partial pressure, and must have sufficient resistivity and excellent properties as a dielectric material for capacitors. What is needed is a dielectric porcelain material that has improved dielectric properties. Examples of materials that meet these conditions include barium titanate solid solutions containing rare earth elements such as Ce, as disclosed in Japanese Patent Publication No. 02-063664. Such a material is a very useful composition because it is not reduced even when fired in a reducing atmosphere, has a small grain size, and exhibits a high dielectric constant.

[0005] As a method for obtaining such a non-reducible dielectric ceramic composition, there is a method of mixing and calcining raw materials consisting of carbonates and oxides to synthesize them.

[0006]

[Problems to be Solved by the Invention] However, with such conventional methods, it is difficult to reduce the raw material itself to 1 μm or less, and therefore it is difficult to obtain a uniform composition even if the raw material is calcined. difficult. When a barium titanate solid solution containing a rare earth element such as Ce is produced by such a method as a non-reducible dielectric ceramic composition, the rare earth element does not diffuse uniformly after calcination, resulting in variations in concentration. When a sintered body is made using this raw material, it is clear that reliability is low when made into a multilayer capacitor in areas with high concentrations of rare earth elements, probably because the non-reducible barium titanate solid solution partially becomes a semiconductor. Became.

Therefore, the main object of the present invention is to obtain a highly reliable multilayer capacitor when producing a multilayer capacitor in the case of obtaining a non-reducible dielectric ceramic composition containing a rare earth element. An object of the present invention is to provide a method for producing a non-reducible dielectric ceramic composition.

[0008]

[Means for Solving the Problems] This invention provides Ba, Sr.
, Ca, Mg at least one selected from A,
At least one selected from rare earth elements R, T
M at least one type selected from i, Zr, and Sn
Then, the following general formula (A1-x Rx )y MO
3, and x and y are 0.001≦x≦0.0
20. A method for producing a perovskite-type non-reducible dielectric ceramic composition satisfying the relationship 1.002≦y≦1.03, using a water-soluble rare earth element inorganic compound or an organic solvent-soluble rare earth element organometallic compound. , a method for producing a non-reducible dielectric ceramic composition.

[0009]

[Operation] By using a water-soluble rare earth element inorganic compound or an organic solvent-soluble rare earth element organic compound as the rare earth element, the rare earth element is uniformly dissolved and diffused in the perovskite type composition.

Here, the general formula (A1-x Rx )y
The reason for limiting x and y of the non-reducible dielectric ceramic composition represented by MO3 will be explained. In other words, x is 0
．． If it is smaller than 001, no reliability improvement effect is observed, which is not preferable. Moreover, when x exceeds 0.02, reliability decreases, which is not preferable. y is 1.002
If it is smaller, it is undesirable because it is more likely to be made into a semiconductor and the reliability will be significantly lowered. Moreover, when y exceeds 1.03, sinterability deteriorates, which is not preferable.

[0011]

According to the present invention, a composition in which rare earth elements are uniformly dissolved and diffused can be obtained, so that a highly reliable multilayer ceramic capacitor can be obtained when a multilayer ceramic capacitor is manufactured. Therefore, compared to a multilayer ceramic capacitor using a conventional dielectric ceramic composition, the thickness of the ceramic element portion between the internal electrodes can be significantly reduced. Therefore, it is possible to make the multilayer ceramic capacitor smaller and larger in capacity. Further, since this non-reducible dielectric ceramic composition is non-reducible, base metals can be used as the internal electrode material, and manufacturing costs can be lowered compared to those using noble metals.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments.

[0013]

[Example] First, raw materials with a purity of 99.8% or more were prepared in Table 1.
A total amount of 1500 g was prepared in the proportions shown below. This raw material is 3
000 cc of pure water and 1 mol% equivalent of CeCl3
and put it in a resin pot. The mixture was then ground and mixed for 16 hours using 5,000 g of zirconia grinding stones with a diameter of 5 mm. The slurry thus obtained was evaporated and dried to obtain a dry powder. 1100 ml of this dry powder
It was calcined at ℃ to obtain calcined powder I in which Ce was uniformly dispersed.

[0014]

[Table 1]

Next, a total of 1500 g of raw materials having a purity of 99.8% or higher were prepared in the proportions shown in Table 2. This raw material was placed in a resin pot along with 3000 cc of pure water. And 5000 g of zirconia crushing stones with a diameter of 5 mm.
The mixture was ground and mixed for 16 hours. The slurry thus obtained was evaporated and dried to obtain a dry powder. This dry powder was calcined at 1150°C to obtain a calcined powder. 1000 g of this calcined powder was placed in a resin pot along with 2000 cc of pure water, 3.0 g of surfactant in terms of active ingredients, and Sm(NO3)3.6H2 O in an amount equivalent to 0.5 mol%. The mixture was then ground and mixed for 16 hours using 5,000 g of zirconia grinding stones with a diameter of 5 mm. The slurry thus obtained was evaporated and dried to obtain a dry powder. By calcining this dry powder at 1150°C, calcined powder II in which Sm was uniformly dispersed was obtained.

[0016]

[Table 2]

A total of 1500 g of raw materials with a purity of 99.8% or higher were prepared in the proportions shown in Table 3. This raw material was placed in a resin pot along with 3000 cc of pure water. And 5000 g of zirconia crushing stones with a diameter of 5 mm.
The mixture was ground and mixed for 16 hours. The slurry thus obtained was evaporated and dried to obtain a dry powder. This dry powder was calcined at 1150°C to obtain calcined powder III.

[0018]

[Table 3]

A total of 1500 g of raw materials having a purity of 99.8% or more were prepared in the proportions shown in Table 1. This raw material is 300
It was placed in a resin pot together with 0 cc of pure water and CeO2 powder equivalent to 1 mol%. Then, a calcined powder IV to which Ce was added using the conventional solid phase method was obtained through the same process as that of the calcined powder I.

[0020] 200 g of calcined powder I was placed in a resin pot with an appropriate amount of organic solvent and organic binder.
Using 2000 g of millimeter zirconia crushing stones,
The mixture was mixed for 10 hours to obtain a slurry. Similarly, slurries were obtained using calcined powder II and calcined powder IV. Further, an amount of Nd(CH3 COCHCOCH3)3 corresponding to 1.5 mol % was added to 200 g of calcined powder III, and this was placed in a resin pot together with an appropriate amount of an organic solvent and an organic binder. Then, using 2000 g of zirconia grinding stones with a diameter of 5 mm, the mixture was mixed for 10 hours to obtain a slurry.

[0021] Using each of the obtained slurries, a casting method using a doctor blade was performed to form a film with a thickness of 15 μm.
A ceramic green sheet of m was produced. On this ceramic green sheet, a paste for internal electrodes using Ni powder was screen printed using a conventional method for manufacturing multilayer ceramic capacitors. Ceramic green sheets printed with paste for internal electrodes were stacked so that the number of layers was 10, and they were integrated by hot pressing to obtain a laminate. Thereafter, this laminate was cut into predetermined dimensions to produce green chips.

[0022] The obtained raw chips were held in an atmosphere of a temperature of 300°C and an oxygen partial pressure of 100 ppm for 2 hours to remove the binder. The raw chips subjected to the binder removal treatment were fired at 1250 to 1300°C for 2 hours in a reducing atmosphere adjusted to an oxygen partial pressure of 3 x 10-8 to 3 x 10-10 atm to obtain a sintered body. . This sintered body was attached with an external electrode and used as a sample. Note that the sample produced using calcined powder I was referred to as sample I. Similarly, calcined powder II, III, I
The samples using V were designated as samples II, III, and IV, respectively.

[0023] Regarding the obtained samples I, II, III, and IV, the capacitance, dielectric constant (ε), dielectric loss (tan δ)
, measure insulation resistance and mean time to failure (MTTF),
It is shown in Table 4. Note that the capacitance and dielectric loss are 1k
The measurement was performed by applying an alternating current voltage of Hz, 1 Vrms. Further, the dielectric constant was calculated from the capacitance by measuring the electrode area and the distance between the electrodes. Furthermore, the mean failure time is a value measured under the condition of applying a DC electric field of 64 V/10 μm in an atmosphere of 150° C. Also,
Regarding insulation resistance, its logarithm value (logIR) is shown.

[0024]

[Table 4]

[0025] As can be seen from Table 4, in sample IV consisting only of calcined powder obtained by the conventional solid phase sintering method,
The mean failure time is short at 1.2 hours, and the reliability is poor. On the other hand, as shown in the present invention, samples I, II, and II are made of ceramic compositions manufactured by using a water-soluble inorganic compound or an organic-soluble organometallic compound as a rare earth element.
It can be confirmed that sample I has an average failure time that is 10 times or more as compared to sample IV.

Claims (1)

[Claims] [Claim 1] At least one selected from Ba, Sr, Ca, and Mg is A, at least one selected from rare earth elements is R, and at least one selected from Ti, Zr, and Sn is M. Then, the following general formula (A1
-xRx)yMO3, where x and y satisfy the following relationships: 0.001≦x≦0.020 1.002≦y≦1.03 Production of a perovskite-type non-reducible dielectric ceramic composition A method for producing a non-reducible dielectric ceramic composition using a water-soluble rare earth element inorganic compound or an organic solvent-soluble rare earth element organometallic compound.